21 October 2012

A team at the Beijing National Laboratory for Molecular Sciences (BNLMS), Chinese Academy of Sciences reports a new method to construct binder-free silicon/graphene electrode materials for Li-ion batteries with high capacity, superior rate capability and strong cycle life. A paper on their work is published in the journal Nano Research.

The binder-free, spin-coated Si nanoparticles/graphene (SC-Si/G) electrode shows a high capacity of 1611 mAh g-1 at 1 A g-1 after 200 cycles, a superior rate capability of 648 mAh g-1 at 10 A g-1, and a cycle life of 200 cycles with 74% capacity retention.

Energy storage has become a critical technology for large scale applications including portable electronics, electric vehicles (EVs), and utility grids...To further improve the energy density of LIBs, the development of new electrode materials with higher capacity or voltage plateau are essential. As for anode materials, silicon stands out as a very attractive candidate in merit of its low lithium-uptake potential (<0.5 V vs Li+/Li) and the highest theoretical capacity (4200 mA h g-1), which is 10 times higher than those of the commercial graphite anodes. Furthermore, silicon is low cost, abundant in nature, and beneficial in mature mass production.

However, the practical applications of Si as anode materials have been severely hampered by two major problems. First, substantial volume changes (>300%) during lithium insertion and extraction from Si result in dramatic pulverization of Si and loss of electrical contact between Si and conducting networks, such as carbon black, leading to a rapid capacity fading upon extended cycling. Second, the huge volume changes will destroy solid electrolyte interphase (SEI) films on the surface of Si, resulting in the Si to be repeatedly exposed to the electrolyte. This causes a continuous formation of SEI films and consumption of the electrolyte and lithium ions. The excessive growth of SEI films lead to higher resistance for lithium ion transportation, lower electronic conductivity, and worse Coulombic efficiency of the Si-based anode. Consequently, the cycling performance will be significantly impaired.

—Zhou et al.

Numerous research groups are working on solutions to those barriers to commercialization, including the use of various Si nanostructures and carbon-coated Si nanocomposites. In their work, Zhou et al. from BNLMS propose a simple and efficient fabrication procedure. Using a stable suspension of Si nanoparticles and graphene oxide in ethanol as a starting point, they use spin-coating to cast a composite film of Si/graphene on a copper (Cu) foil, which can later on be directly used as anode with the film as the active material while the Cu foil as the current collector.

The SC-Si/G electrode shows several advantages compared to Si electrodes prepared in more conventional ways, the team suggests:

The facile solution-based spin-coating technique can be successfully applied to prepare high quality Si/graphene films with favorable structures for its application in LIBs. Proper treatment of Si nanoparticles results in their stable dispersal in ethanol, making the spin-coating technique possible.

The existence of graphene in the electrode acts as both an efficient electronic conductor and effective binder. No binder, such as polyvinylidenefluride (PVDF) or polytetrafluoroethylene (PTFE), is needed for the formation of a high-performance Si/graphene film benefiting from the high flexibility of graphene sheets, which can effectively cover and permeate through the Si nanoparticles.

The film has a unique nanostructure that can accommodate the large volume changes of Si nanoparticles during cycling, improve electronic conductivity of Si nanoparticles via the graphene, and possess enough void spaces around the Si nanoparticles for lithium ion diffusion and volume expansion of Si nanoparticles.

This successful materials design for Si-based anode could also be extended to other high capacity anode and cathode materials with large volume changes for advanced LIBs, the authors conclude.

Comments

I think the point about this paper that is significant is the fact there is a lot of research going on in improving EV batteries; but, it's not extensively happening here. It's mostly taking place in Asia.

While we suffer with yet another two year election process fighting over oil policy (financed by Big Oil) and our profit motives, they are spending their money getting things done. I look for most battery advances to come from China, Japan, and Korea, not from our country. BTW, is there a U.S. battery company that sells Li batteries directly to DIYs? I don't think so and why do you think that is? Control of the market perhaps?

Yes Lad...the expressed need for a product (such as improved lower cost batteries) is not enough for the product to be mass produced. A meaningful home majority must develop the will to do something about it and specially to counteract the blocking efforts and propaganda being thrown at us by Big Oil and their puppet politicians.

The situation is very different in China-South Korea-Japan-Irael and many other Asian countries. Those countries have real on-going shortages of liquid fuels for their fast growing economy. Importing Oil at $100+/barrel is not a sustainable solution. They cannot rely on local production and the immediate neighbors (like USA with cheap oil from Canada-Mexico-Venezuela etc). Their government, including official opposition where allowed, support the accelerated development of lower cost higher performance batteries for early transition from ICEVs to electrified vehicles.

The same could be said about high speed e-trains. China and EU are building 200,000+ Km of electrified railroads and will soon have thousands of very high speed e-trains while USA and Canada may have 500 Km with relatively low speed e-trains.

Falling behind on the economic and development fields may be indicative of the beginning of the end of an era? It may be so?

Improved performance, next generation, lower cost, mass produced batteries for practical highway EVs should reach the market place sometime between 2017 and 2022. Soon thereafter, it will become a $300B/year to $500+B/year business. Chances are that the majority could be produced in Asia, unless we find ways to do it at lower price?

Is it a never ending story or what. As soon as they improve some parameters then there is drawbacks like this one where they found 300% volume change and loss of electrical contact.

If it continue like that, i might never buy for myself an electrical car. I will be born under the ice car era and die without driving and owning a car powered by clean efficient more torquey electricity.

Actually costs and specifications for electric car are simply not there yet. The range at minimum should be for 12 hours of driving without interruption. Now , even with a tesla at 110 000$ the range is barrelly 3 hours. With results like that serious buyers will never buy electric cars or trucks like tAXI DRIVERS, truckers, racers, long distance tourists, blue collar workers. In 2022, when i'll be ready to change my actual car, there won't be anything new on the market and i will still rely on a small well maintain gasoline car.

Each and all of these new technologies are costly, underperforming and to date no profits have been made.
Batteries, biofuels, synthetic fuels, chimical fuels like hydrogen or synthetic natural gas, windmills power accumulation, etc, all of these new things are a huge dissapointment with less then promising results. I was betting on hydrogen in the past, but since months they seam to get to a dead end with that and they don't speak anymore about hydrogen. In the future they will stop battery, fuels and hydrogen and every researchs because they never find anything worth commercialising.

gorr, we can recognise you whether you call yourself AD or ab or whatever.
Still the same old delusional rubbish.
I have not criticised you before, however nonsensical your posts, but if you are going to multiple identities now your nuisance value is increasing and you are starting to merit complaints.

No the practical energy density has ever been more than 40% theoretical for most battery chemistries. Something to think about when making pie in the sky predictions for future lithium ion energy density.

Hey Davemart,
LOL You have to give gorr credit, he's getting more creative these days with the multiple IDs.

I think we're still a good 7-8 years off from a viable, all electric car, and I still have hope we'll get there. I'm even willing to concede that may be an H2 fuel cell car, just don't know at this point. I still hope for that battery breakthrough that will allow a simple, BEV to meet needs, but it would need a breakthrough. Sigh.

But you gotta love gorr: 12 hours of uninterrupted driving? My god, you'd be crippled and need a to wear a diaper! LOL What would even be the point?

There is ultimate solution on the market which keeps promises-Chevrolet Volt. US transportation based on this technology could be 100% oil free. Thats why Big Oil and related politocans oposing this development so heavily.

Hi DaveD.
If we do get a wonderful all singing and dancing battery, well and good.

In cars like the Toyota the pack is exactly the same as the one which will be the first production model, so there is no new development needed to go to that, although further improvements for later models are certainly possible and undergoing development.

The fuel cell car for a given weight and range is fundamentally better than a battery car with the batteries we can do, as it is lighter.

Of course, if we ever get to the point of building electric roads, then only a 12kwh or so battery pack would be needed, and efficiency is better yet.

Zapping the power in in the fractions of a second the car would be over the charger is non-trivial though, so like super batteries, and methanol fuel cells which would have substantial advantages over hydrogen ones should not be counted on.

Given the dire sales to date of electric cars and the durability problems of the packs used in the most common one, the Leaf, at the moment hydrogen fuel cells seem like the the best practical option for other than small city cars.

Car salesmen have been selling cars for years based on that once a year need a family has for a long range vehicle. the family vacation. If you take that out of the mix and decide to rent a car for those times you really need range, perhaps an EV will work for you.

My Leaf costs me less than $20k after incentives and fits our life style easily because we are retired and drive short distances to shop in nearby cities. Our few long distance drives are handled by a Pickup or when I plan about three hours to re-charge on the road.

I do not see economic rationale jumping from PHEV to BEV unless gasoline or liquid fuel would be $40/gal. PHEVs do not require investments into infrustructure and more than 70% of distance could be covered on electricity alone. The rest 30% could be subject for various types of synthetic and biofuels and range extenders could be very flexible on that.

PHEV for light duty vehicle is ultimate solution for hundred years ahead unless cost of batteries will drop 10 fold and average standard useful capacity would be above 100 kWh (300 lbs).

Darius:
The PHEV using a combustion engine is a good stop gap, but is inherently complex with a high part count:
http://www.electricauto.me/Learning.html

You are still lugging around an engine, high temperature exhaust system and so on, but only using it part time.

In contrast an electric car, whether powered by batteries, fuel cells or both, is simplicity itself with a unified design and a much lower parts count.

Much is made of the supposed lower efficiency of fuel cell vehicles against batteries, but there is little comment on the great improvement fuel cells make on petrol cars.

Fuel cells are around twice as efficient as combustion engines, and there are plenty of losses in refining petrol as well as producing hydrogen from natural gas and compressing it, so overall the efficiency is better, with the difference that a dependence on imported and increasingly scarce and expensive oil is eliminated.
That is beside from the possibility of producing hydrogen from much more long lasting renewable or nuclear sources.

Outside of the US not such a big deal is made of replacing infrastucture, and we now have decent cost estimates, around 1 million Euros for a hydrogen station at the moment, reducing with volume to around the same price as a natural gas station to maybe 330,000 Euros,

The notion that hundreds of millions of cars will continue to carry around heavy engines and combustion engine fittings like exhaust systems for evermore because that infrastructure can't be installed makes no sense.

For small city cars it is pretty clear that batteries will be able to do the job just fine within the next few years, so again you don't need a PHEV.

They are what we need at the moment, but all the car companies as well as the DOE etc realise that we will need to move on later.

I am still convinced HEVs soon, and BEVs soon after will take the low-cost-of-ownership crown from the ICE, but it is painfully slow - and getting costly.

The likelihood that batteries are nearing their peak is very low - they will likely overtake the ICE.

But why should private industry or government invest in a product (such as improved lower cost batteries) if the expressed need for a product is not enough for the product to be mass produced?

#1. Are not batteries for EVs in various forms already selling by the many millions? Already mass produced?

#2. We have poured good money after bad for 10+ years with rebates, grants and loan guarantees because politicians did not know nor care that there was a proper time to invest.

#3. If the R & D effort is moving to Asia now (I do not think it is) it is partly because we have spent to much in a wasteful manner and (like Germany with its wind power) it is becoming no longer "in" with anyone but the kindergarten teachers.

#4. What kind of tin hatted loonies believe (and why) that blocking efforts and propaganda are being thrown at us by Big Oil and their puppet politicians and that it is holding battery research back?

Many new technologies have been kept in the back room for years and decades to favor older (high profit) inefficient technologies. Industries will not normally change a winning (high profit) product unless they are forced to do so.

Radial tires, front wheel drives, modern higher efficiency diesel engines, improved A/C, LED automobile lights, USB plugs on car radios, etc were delayed for many years and decades in North American cars to benefit the Big-3 bottom line.

The Big-3 had the nerve to falsely tell us that those technologies were not for our roads, climate etc in order to push their lemon-rusting boats on wheels. They were forced to change when much better cars from Japan and EU were imported and took a very large share of the traditional home market.

BYD's (China) excellent batteries with over 4000 cycles, their excellent long range (300 Km) e-taxis (E-6+) and their excellent large e-city buses already have worldwide markets.

First generation electrified vehicles would have stronger impacts (per vehicle) as e-taxis and e-city buses to clean up city cores from air pollution and noise etc.

Massive private ownership of e-vehicles may have to wait for next generation batteries with 600+ Wh/Kg capacity and much lower price per kWh. Those e-vehicles equipped with 100+ kWh batteries would have 600+ Km range between charges and would satisfy most users. That may not happen before 2017/2018/2-19?

Lad: You asked about a US battery company that sells directly to DIYs. Although they are an Asian based company, CALIB Power in California sells their LiFePO4 cells directly to consumers. I bought cells for an electric vehicle conversion I completed last winter.